ISP lookup showing wrong data!

I'm completely tearing my hair out trying to debug a critical issue with our "What is My ISP?" web tool. For the past 48 hours, our ISP lookup functionality, which relies heavily on accurate IP address lookup, has been showing wildly inaccurate results for a significant portion of our users, and I'm at my wit's end.

• The Problem: Our tool is designed to accurately identify a user's Internet Service Provider. However, for many mobile users, especially on specific carriers, it's consistently returning incorrect ISP data. Instead of showing the actual mobile carrier (e.g., T-Mobile, Verizon), it frequently displays data center providers or generic backbone ISPs, like "Google Cloud" or "Amazon Technologies," which is completely wrong. This is severely impacting user trust and the utility of our tool.
• What I've Tried (and Failed At):
  • I've integrated and cross-referenced results from multiple reputable IP geolocation APIs (e.g., ipapi.com, ip-api.com, and even MaxMind GeoIP2 locally). All of them seem to return similar, incorrect data for the affected IPs.
  • I've meticulously checked our server-side code (Node.js backend) for any caching issues, misconfigurations in how we pass IP addresses, or any potential conflicts. Everything seems by the book.
  • I've tested the tool myself using various mobile networks, both directly and through VPNs. While VPNs usually give expected results (the VPN provider's ISP), direct mobile connections often fall into the "wrong ISP" category.
  • I've looked into DNS resolvers for the problematic IPs, but that hasn't shed any light on why the ISP itself is misidentified.
  • I've also compared our results against other popular "What is my IP" and "ISP lookup" tools online, and frustratingly, many of them show similar inaccuracies for the same test cases. This makes me think it's not *just* my code, but something more fundamental.
• Specific Observations:
  • The issue seems most prevalent with mobile ISPs, particularly in certain regions.
  • Desktop users on fixed-line broadband connections rarely experience this problem; their ISPs are usually identified correctly.
  • It's not 100% of mobile users, but a significant enough percentage to be a major concern.
• My Desperate Plea: Has anyone encountered this specific kind of ISP lookup inaccuracy, especially concerning mobile networks and their IP handling? Could this be related to Carrier-Grade NAT (CGNAT) and how different IP databases interpret those shared IPs? Are there any less common but highly accurate IP geolocation or ISP identification APIs I should be looking into? Any specific debugging steps or server-side configurations I might be overlooking? I'm completely stuck and need fresh eyes on this. Any advice, no matter how small, would be a lifesaver. Thanks in advance!